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Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 7(1): 35- 44
© Scholarlink Research Institute Journals, 2016 (ISSN: 2141-7016)
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Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 7(1):35-44 (ISSN: 2141-7016)
Geoelectric Delineation of Hydrocarbon Spill in Abesan Lagos,
Nigeria
1
Akinrinade Opeyemi J., 2Oladapo Michael. I, 3Onwah Christopher
1
Department of Marine Science and Technology,
Federal University of Technology Akure, Nigeria,
2
Department of Applied Geophysics, Federal University of Technology Akure, Nigeria,
3
Mutual Benefits Assurance PLC Lagos, Nigeria
Corresponding Author: 1Akinrinade Opeyemi J.,
_________________________________________________________________________________________
Abstract
This study was undertaken at Abesan Estate in Lagos with the aim of determining the spatial and depth extent of
hydrocarbon contamination occasioned by vandalization of petroleum pipeline crossing the area. The area is
underlain by the Benin Formation. The electrical resistivity method was adopted. Sixteen Vertical Electrical
Sounding (VES) stations were occupied with two horizontal profiles using Schlumberger and Wenner electrode
arrays respectively. Three to four geoelectric layers were delineated from the VES curves interpretation, with
resistivity varying from 46 - 249 Ωm for the topsoil, 2.5 - 166 Ωm for the second geoelectric unit, 387 – 17,192
Ωm for third geoelectric unit; and thicknesses of 0.8 - 2.8 m, and 1.3 - 7.1 m for the topsoil and second layer
respectively. Iso-resistivity depth slices generated from 1 to 6 m enabled the establishment of lateral and vertical
distribution of the hydrocarbon contamination plume and identification of the contaminant migratory pathway.
The unconfined hydrogeologic setting of the subsurface sequence has likewise enabled the downward migration
of the hydrocarbon spill to depth of 5 – 6 m as observed in relatively high resistivity values characterizing the
layers. The resistivity distribution pattern indicates migration towards the northern flank while the contaminant
source is on the southern edge. The aquifer in the area is overlain by materials of weak protective capacity (0.03
– 1.12 mhos) with fairly high anisotropy (1.03 ≤ λ ≤ 4.22). Thus, shallow aquifers in Abesan Estate and the
adjoining areas are under severe threat of hydrocarbon contamination.
__________________________________________________________________________________________
Keywords: hydrocarbon, contamination, aquifer, geoelectric, migration, protective capacity
With poor maintenance, some of the surface pipes
leaks serve as conduit for hydrocarbon spillage into
the environment. This type of contamination is
undoubtedly one of the environmental challenges
being grappled with in recent times.
INTRODUCTION
Environmental challenges which affect the
groundwater system are of various types. Such
challenges could be contamination occasioned by
hydrocarbon spill from pipelines, leachate from
dumpsites, industrial waste etc. Groundwater
contamination as a result of hydrocarbon spill from
pipelines is a common phenomenon in some areas
with pipeline crossing. Hydrocarbon spill from
pipeline could be caused by several factors which
include blowouts resulting from overpressure,
equipment failure, operators errors, corrosion,
vandalization, pigging operations, flow line
replacement errors, flow station upgrades, tank
rehabilitation and natural phenomena such as heavy
rainfall, flooding, falling of trees, lightening and poor
management practices around oil installation
(Ozumba et al., 1999; Atakpo and Ayolabi, 2008).
When spills occur, the groundwater or aquifer
systems as well as the soil in such environment
remain at risk of contamination. The impact on the
groundwater aquifer system usually constitutes health
hazards to inhabitants of such environment who
depend on groundwater as a major source of potable
water supply. Most of these pipelines that now pass
through the cities are exposed due to gully erosion.
It is true that oil spills can occur due to a variety of
reasons (Ozumba et al, 1999), of these many reasons,
sabotage (pipeline vandalization) remains a major
cause. After an oil spill has occurred, it is often
desirable to determine the spatial and depth extent of
the contamination. In having to do this, carefully
designed geophysical approach plays a significant
role. Geophysical studies afford the opportunity of
non-invasively evaluating the extent of existing
contamination, predict the trend of the contamination
plume within the subsurface, possibly guide
exploratory drilling programmes and provide a guide
to the remediation technique that should be
employed.
The Electrical Resistivity method amongst several
other geophysical methods has been used to solve
environmental problems (Shevnin et al., 2005; Tse
and Nwankwo, 2013; Atakpo, 2013). Noteworthy is
that the success of the electrical resistivity method in
35
locating oil contaminant plumes depends on the size
and shape of the plume and the resistivity contrast
between the native groundwater and the invading
fluid, amongst other factors. Aquifer contamination
caused by liquid effluents from oil can thus be
detected, mapped and modelled using resistivity
methods (Busseli et al, 1990; Baker, 1990; Bauman et
al, 1993).
Government Area of Lagos State, Nigeria (Figure
1a). In 1993, oil spill (consequent to vandalization of
pipelines conveying petroleum products) polluted the
water bearing aquifer of the Baruwa community. The
groundwater
in
Baruwa
community
was
contaminated by petroleum products from the leaking
pipes, a situation which rendered water from their
wells and boreholes unsafe for domestic use.
When a spill occurs, hydrocarbons commonly
migrate downward through the soil column and
accumulate as a lens above the water table (Davies et
al, 1992). Some of the factors which influence the
migration in the subsurface include rainfall,
groundwater level and hydraulic gradient (Daniels et
al, 1995). Hydrocarbon spills which originate from
underground tanks are normally referred to as Light
Non-Aqueous Phase Liquid (LNAPL) in capillary
fringe above the water table and as Dense NonAqueous Phase Liquid (DNAPL) below the water
table (Subba and Chandrashekhar, 2014)
The estate (Figure 1b) occupies an area extent of
about 550,000 square meters and lies within latitude
ranges of N06⁰ 36ʹ 19.0ʹʹ and N06⁰ 36ʹ 44.2ʹʹ and
longitude ranges of E003⁰ 16ʹ 15.0ʹʹ and E003⁰ 16ʹ
25.6ʹʹ. It is a residential area consisting basically of
blocks of flats and few shops. The major source of
water is groundwater abstracted via boreholes, as
several boreholes could be sighted adjacent to several
buildings.
During the reconnaissance survey, parts of the estate
were observed to be faced with this environmental
problem while some other parts are free of it. This
information guided the field survey design.
The magnitude of the apparent resistivity anomaly
value is dependent on the proximity to the spill.
Cultural interferences and the thinness of the oil body
were significant factors making delineation difficult
(Andres and Canace, 1984).
GEOLOGY AND GEOMORPHOLOGY
The geologic successions in Lagos spans through the
Cretaceous
Abeokuta
Formation,
which
unconformably overlies the rocks of the Basement
Complex, to the Quaternary deltaic Plain Sands.
Alimosho within which the survey area is located is
directly underlain by the Benin Formation (Figure 2,
Table 1).
In some cases, hydrocarbon polluted soils are
characterized by high resistivity. However, it should
be emphasised that these have been observations
from laboratory studies conducted or studies
conducted on newly polluted sites. In cases of aged or
matured contaminations, high resistivity has been
attributed to factors such as existence of clayey layers
which had hindered microbial activity. Low
resistivity values have been recorded in older or
matured (few weeks to few years based on other
surrounding factors) polluted sites (Mohammad et al.
2011, Subba and Chandrashekhar, 2014). Benson and
Mustoe (1998) have attributed hydrocarbon plume
(both dissolved and free-product) to area of high
resistivities using both GPR and Electrical Resistivity
(ERI) Imaging techniques. Low resistivity attribute
values associated with hydrocarbon contaminated
clayey sand is attributed to biodegradation of the
crude oil (Tse and Nwankwo, 2013). Hydrocarbon
becomes heavier after undergoing biodegradation
(Bailey et al, 1973) and therefore tends to settle
below the groundwater level (Modin et al, 1997).
The Benin Formation consists largely of
sands/sandstones with lenses of shale and clay. It
provides a ready answer to the groundwater problems
of a good portion of Lagos State especially where it is
characterised by pebbly beds. Noteworthy, however
is that the arenaceous nature of the Benin Formation
makes it susceptible to contamination from
anthropogenic sources. The Ilaro Formation consists
of fine to coarse sands alternating with shale and
clay. This formation though consisting of aquifers,
can
only
sustain
poor
boreholes.
The
Ewekoro/Akinbo/Oshosun formations consist of a
sequence of sandstones, shales, Limestones and
clays. Though the Ewekoro Formation could consist
of several aquifers, its argillaceous nature
recommends it as being of poor groundwater
potential.
The aim of this research work is to establish the
general aquifer system characteristics of the survey
areas within Abesan Housing Estate, Lagos Nigeria
and determine the spatial and depth extent of
contamination in the affected areas.
The Abeokuta Formation consists of Arkosic
sandstones and grits, tending towards being
carbonaceous at the base. This formation has good
potential for groundwater except that the bituminous
materials associated with the sands could possibly
affect the quality of the water. Noteworthy is that all
these formations are multi-aquiferous.
LOCATION DESCRIPTION
Abesan Estate, Ipaja is a residential housing estate
located within Baruwa community in Alimosho Local
36
Geomorphologically, the study area is characterized
by a gentle topography. The dominant vegetation of
this area is the swamp forest of the coastal belt which
is influenced by the double rainfall pattern.
RESULTS AND DISCUSSION
The results of this work are presented as VES curves
for the Schlumberger electrode configuration, and
Pseudo-sections for the Horizontal Profiles. From the
VES results, resistivity maps at varying depths were
generated to identify possible migrating plume
pathway. Further to this, Dar Zarrouk parameters
namely longitudinal unit conductance (S), transverse
unit resistance (T) and coefficient of anisotropy (λ)
were determined.
The climate in Lagos within which the study area is
located is similar to that of the rest of the southern
Nigeria. Average temperature highs and lows for
Lagos are 31°C and 23°C in January and 28°C and
23°C in June. The mean annual precipitation is about
1,900 mm.
The results show a subsurface sequence consisting of
three to four geoelectric layers. The curve types
characterizing the survey area are A, AK, H, and HK
(Figure 4, Table 2). Four layers were identified at
VES 7 and 8. The interpreted underlying units are
topsoil, clay, clayey sand and sand.
METHODOLOGY
The Direct Current (DC) electric resistivity method
was adopted for this study.
The Vertical Electrical Sounding (VES) was used to
determine the variations of resistivity with depth,
while horizontal profiling was used to determine
lateral
resistivity
variation.
Wenner
and
Schlumberger electrode arrays were adopted
respectively (Figures 3a and b). The materials used
include R-50 resistivity meter and Garmin 80 Global
Positioning system.
The resistivity values characterizing the topsoil
(Figure 5) range between 46 and 249 Ω-m, while
thickness range between 0.8 and 2.8 m. Generally,
the resistivity values are higher in the north-western
flank.
The resistivity values characterizing the second
geoelectric unit (Figure 6) is generally low, with
values ranging between 2.5 and 166 Ω-m. The
highest value is recorded on the western flank of the
area. The low resistivity values are indicative of
presence of clay constituents within the unit. The
thickness values range between 1.3 and 7.1 m.
Sixteen (16) VES stations and two (2) horizontal
profiles were occupied. The maximum current
electrode spread for the Schlumberger electrode array
is 150 m (AB/2), while the potential electrode
separation maximum is 10 m (MN/2). The Wenner
inter-electrode separation (a) was varied through 15,
30, 45, and 60 m while total profile length of 270 m
was covered.
The resistivity values characterizing the third
geoelectric unit is considerably high except for areas
around VES 2, VES 7 and VES 8 (Figure 7). The
values range between 387 and 17,192 Ω-m. The
highest value was recorded in the north-eastern flank
of the area, while the south and north-west recorded
low values.
Second-order geoelectric parameters (Dar Zarrouk
parameters) were determined from primary
geoelectric parameters of layer resistivity values and
thicknesses. The relationships are:
(1)
Iso-resistivity depth slices at 1, 2, 3, 4, 5 and 6 m are
presented in Figure 8. The map shows resistivity
distribution laterally and vertically to monitor
possible three dimensional (3-D) hydrocarbon
contamination plume migratory pathway within the
study area.
(2)
(3)
(4)
(5)
At 1 m depth, low resistivity values characterize the
entire horizon. The low resistivity values indicate
none or limited existence of hydrocarbon pollutant
due to percolation occasioned by precipitation.
However, clay constituents within the top layer
cannot be ruled out.
For n layers,
(6)
(7)
- Longitudinal unit conductance,
unit resistance,
resistivity,
- Layer thickness,
-
Anisotropy
Longitudinal resistivity,
- Transverse
At 2 m depth, the resistivity is observed to be
generally low due to reasons advanced for the top
layer.
– layer
coefficient,
-
- Transverse resistivity,
At 3 m depth, a localised high resistivity is observed
around VES 4 on the north-eastern part of the area.
- conductivity
37
However, low resistivity values dominate the
southern part.
the oil spillage from pipeline conveying refined
hydrocarbon products. The subsurface geologic
sequence underlying the environment comprises the
topsoil, clay substratum/clayey sand and sand
bedrock. The sandy bedrock constitutes the aquifer.
The aquifer in the area is unconfined with fairly high
vulnerability.
Low resistivity values are predominant at 4 m depth,
as observed on the western flank (Figure 8). Thus, it
could be inferred that the hydrocarbon spill which is
presumably high resistivity associated has percolated
and is still retained within the layer.
The unconfined hydrogeologic setting of the
subsurface sequence has enabled the downward
migration of the hydrocarbon spill to depth of 5 – 6 m
as presented in relatively high resistivity values
typing the layers. The resistivity distribution
configuration indicates migratory pathway towards
the northern flank while the contaminant source is on
the southern edge.
High resistivity characteristics are predominant at 5
and 6 m horizons. The resistivity distribution outlay
indicates migratory pathway in the northern direction
with a source located on the southeastern edge. Thus,
with the knowledge of the pipeline route passing the
southeastern flank of the study area, the contaminant
effect is expectedly dominant around the area.
Second order parameters were computed to further
elucidate on the hydrocarbon spill effect (Table 3).
Longitudinal unit conductance (S), longitudinal
resistivity (ρ L), and coefficients anisotropy (λ) were
determined. The protective capacity is considered to
be proportional to the longitudinal unit conductance
(Olorunfemi et al., 1998; Oladapo et al., 2004;
Ayolabi, 2005 and Atakpo and Ayolabi, 2008).
The aquifer in the area is overlain by materials of
weak protective capacity (0.03 – 1.12 mhos) with
fairly high anisotropy (1.03 ≤ λ ≤ 4.22). The study
has brought to knowledge the need to encase
pipelines passing the area in water tight concrete to
prevent spillage.
REFERENCES
Andres, K. G. and Canace R. 1984. Use of the
electrical resistivity technique to delineate a
hydrocarbon spill in the coastal plain deposits of New
Jersey. Proceedings of the NWWA/API Conference
on Petroleum Hydrocarbons and Organic Chemicals
in Ground Water: Prevention, Detection and
Restoration; National Water Association, Dublin,
Ohio. Pp 188-197
The results of the longitudinal conductance show
values in the range of 0.03 and 1.12 mhos (Figure
9a). The higher values are found on the southern part
of the study area. Adopting the longitudinal unit
conductance classification of Henriet (1976) and
Oladapo et al., (2004) the aquifer protective capacity
rating varies from poor to good. The results further
establish that the underlying aquifer could be
infiltrated by polluting fluid especially in central and
northern half areas where longitudinal unit
conductance values are lower than 0.2.
Atakpo E. A. 2013. Resistivity Imaging of Crude Oil
Spill in Ogulaha Coastal Community, Burutu L. G.
A., Delta state, Nigeria. International Journal of
Research and Reviews in Applied Sciences
(IJRRAS). 15 (1): 97-101
The anisotropy coefficient (λ) map (Figure 10) shows
that the southwestern flank of the area is
characterized by high anisotropic materials with a
maximum value of 4.2 with a general reduction in
values northwards.
Atakpo, E.A. and Ayolabi, E.A. 2008. Evaluation of
Aquifer Vulnerability and the Protective Capacity in
some Oil Producing Communities of Western Niger
Delta. Environmentalist Springer. DOI 10.1007/s
10669-008-9193-3.
The results of two Wenner horizontal profiles carried
out on the southern flank are presented as
pseudosections in Figure 11. The models show twodimensional resistivity distribution within the flank.
The resistivity distribution presents characteristically
conductive topsoil (4 – 253 Ω-m) with steady
increase in resistivity (10106 – 26107 Ω-m) with
depth. The upper subsurface low resistivity units are
indicative of shallow clayey materials while the
underlying deeper higher resistivity units may be
attributes of hydrocarbon contaminated medium to
coarse-grained sand units.
Ayolabi, E.A. 2005. Geoelectric evaluation of
Olushosun Landfill Site Southwest Nigeria and its
Implication on Groundwater. Journal. Geological
Society of India, 66: 318-322.
Bailey, N. J. L., Krouse, H. R., Evans C. R., and
Rogers M. A. (1973). Alteration of Crude Oil by
Waters and Bacteria - Evidence from Geochemical
and Isotope Studies. American Association of
Petroleum Geologist Bulletin. 57 (7): 1276 – 1290.
CONCLUSION
Geoelectric study has been undertaken in this work to
determine the level of contamination occasioned by
38
Barker, R. D. 1990. Investigation of groundwater
salinity by geophysical methods. Geotechnical and
Environmental Geophysics. Society Exploration
Geophysics, Tulsa OK, Pp. 201-211.
Researches in Energy, Environment and Landscape
Architecture. Pp 135 – 139
Obaje, N. G. 2009. Geology and Mineral Resources
of Nigeria, Lecture Notes in Earth Sciences 120,
Springer-Verlag Berlin Heidelberg. Pp 221.
Bauman, P., Sallomy, J., Wong, T. and Hardisty, P.
1993. Geophysical data processing techniques as
related to groundwater contamination studies. Proc.
Symposium. Application of Geophysics to
Engineering and Environmental Problems. EEGS,
San Diego, CA. Pp. 167-180.
Oladapo, M. I., Mohammed, M. Z., Adeoye, O. O.
and Adetola, B. A. 2004. Geoelectrical investigation
of the Ondo State Housing Corporation Estate, Ijapo
Akure, Southwestern Nigeria. Journal of Mining and
Geology, 40(1): 41–48.
Benson, A. K. and Mustoe, N. B. 1998. Integration of
Electrical Resistivity, Ground-Penetrating Radar, and
Very Low-Frequency Electromagnetic Induction
Surveys to Help Map Groundwater Contamination
Produced by Hydrocarbons Leaking from
Underground
Storage
Tanks.
Environmental
Geosciences. 5(2): 61-67.
Olivar A. L., Hedison K., and Milton J. 1995.
Imaging industrial contaminant plumes with
resistivity techniques.
Journal
of
Applied
Geophysics. Pg 93-108
Olorunfemi, M.O, Ojo, J.S. and Oladapo, M. I. 1998.
Geological, hydrogeological and geophysical
investigation of exposed 20'' Escravos Lagos
Pipeline. Technical report
Busseli, G., Barber, C., Davis, G. B. and Salama, R.
B. 1990. Detection of groundwater contamination
near waste disposal sites with transient
electromagnetic and electrical methods. Geotechnical
and Environmental Geophysics, Society Exploration
Geophysics, Tulsa, OK, pp. 27-39.
Ozumba C. I., Ozumba M. B., Obobaifo C. E. 1999.
Striking a balance between oil exploration and
protecting the environment. NAPE Bulletin. 14 (2):
130-135.
Daniel J. J., Roberts R. and Vendl H. 1995. Ground
Penetrating Radar for the detection of liquid
contaminants. Journal of Applied Geophysics. 33:
195-207
Shevnin, V., Rodriguez O. D., Luis F., Hector Z. M.,
Aleksandr M., and Alber R. 2005. Geoelectrical
Characterization of an oil-contaminated site in
Tabasco, Mexico, Geofisica International. 44 (3):
251-263.
Henriet, J. P. 1976. Direct application of the Dar
Zarrouk parameters in groundwater surveys.
Geophysics Prospective, 24: 344–353.
Subba R. C. and Chandrashekhar V. 2014. Detecting
oil contamination by Ground Penetrating Radar
around an oil storage facility in Dhanbad, Jharkhand,
India. Journal Industrial Geophysical Union. 18 (4):
448-454
Modin, I. N., Shevnin, V. A., Bobatchev, A. A.,
Bolshakov, D.K., Leonov, D.A. and Vladov, M. L.
1997. Investigations of Oil Contamination with
Electrical Prospecting Methods. Proceedings of the
3rd EEGS-ES Meeting, Aarhus, Denmark. Pp 267270.
Tse, A. C. and Nwankwo A. C. 2013. An integrated
Geochemical and Geoelectrical investigation of an
ancient crude oil spill site in south east Port Harcourt,
Nigeria. Ife Journal of Science. 15 (1): 125-133
Moradi, M., Hafizi, M. K., Taheri, B., and Kamal, H.
S. 2011. Application of Geophysical methods to
delineation of LNAPL contaminated plume. Recent
39
APPENDIX
a
Figure 1: (a) Geological map of Nigeria indicating the study area within Lagos State metropolis (Modified after
Obaje, 2009). (b) Map of the study site.
40
Table 1: Formational succession in the Lagos area
Deltaic plains
Quaternary
Benin Formation
Ilaro formation
Oshosun formation
Ewekoro formation
Abeokuta formation
Basement
Tertiary
Cretaceous
a
P1
C1
a
a
I
Figure 2: Geological map of Lagos showing
Alimosho within which the study area is located
(modified after Offodile, 2002)
b
A
C1
L
I
A
P2
C2
a
M
N
B
P1
P2
C2
2l
M N
I’
L
B
I’
Figure 3a and b: Basic Wenner and Schlumberger
electrode arrays using conventional four electrodes.
C1 and C2 represent the current electrodes and P1 and
P2 the potential electrodes.
Figure 4: VES 1, VES 7, VES 13 and VES 15 sounding curves from the study area.
41
Table 2: Geoelectric parameters and lithology
delineated in the study area
VES
No. of
Resistivity
Curve
Thickness(
Depth(m)
Station
layers
(Ohm-m) ρ1/ρ2/…ρn-1
Type
m)
d1 /d2 /…dn-1
h1/ h2/ h3
1
3
125.6/24.6/17192
H
1.2/1.8
1.2/3
2
3
136.4/14.7/396.1
H
1.5/2.5
1.5/4
3
3
248.5/30.5/8589.5
H
1.2/2.9
1.2/4.1
4
3
106/28.4/14854.9
H
0.9/1.4
0.9/2.3
5
3
80.9/20.7/1755.3
H
1.0/7.1
1.0/8.2
6
3
45.5/88.6/2189.6
A
1.2/5.9
1.2/7.1
7
4
69.9/165.8/387/129.9
AK
1.3/1.3/3.2
1.3/2.6/5.8
8
4
127.5/36.8/616.5/89.9
HK
0.8/1.4/6.1
0.8/2.2/8.3
9
3
61.8/8.1/3326.9
H
1.5/2.6
1.5/4.1
10
3
157.7/9.1/9229.9
H
1.5/1.8
1.5/3.2
11
3
48.4/5.8/4165.1
H
2.8/2.3
2.8/5.1
12
3
234.2/2.5/1466.9
H
0.8/2.5
0.8/3.4
13
3
109.2/3.4/1555.1
H
1.3/3.6
1.3/4.9
14
3
109.4/6/6903.6
H
1.3/3.6
1.3/4.9
15
3
148/13.8/7844.4
H
2.6/2.3
2.6/4.8
16
3
61.2/10.8/4113.5
H
1.5/2.4
1.5/3.9
Figure 5: (a) Isoresistivity map of layer 1 (b)
Thickness map of layer 1
42
Figure 8: Isoresistivity depth slice for surface, 1m,
2m, 3m, 4m, 5m, and 6m depth
Figure 6: (a) Isoresistsivity map of Layer 2 (b)
Thickness map of layer 2
Table 3: Dar Zarrock Parameters estimated for the
study area
Longitudinal Transverse Longitudinal Transverse Anisotropy (λ)
VES Conductance Resistance Resistivity Resistivity
No
S (mhos)
T (Ω)
ρL (Ωm)
ρT (Ωm)
36.2648
1
0.0827
195
65
1.3388
60.3375
1.6527
94.3049
1.5159
58.7652
1.2151
28.1321
1.1109
81.3155
1.0319
266.3466
1.2625
471.5867
1.7551
27.7463
1.5286
76.6455
2.1943
29.1882
1.6126
58.6697
4.2237
30.3686
2.5935
33.4327
2.0433
85.0082
1.7878
30.1846
1.3819
22.0915
2
0.1811
241.35
41.0365
3
0.0999
386.65
39.8018
4
0.0578
135.16
22.7940
5
0.3554
227.87
76.3728
6
0.0930
577.34
167.1108
7
0.0347
1544.81
8
0.0542
3914.17
153.1011
11.8751
9
0.3453
113.76
15.9179
10
0.2073
252.93
11.2235
11
0.4544
148.86
3.2888
12
1.0034
193.61
4.5151
13
1.1296
154.88
8.0081
14
0.6119
163.82
26.5966
15
0.1842
416.54
15.8066
16
Figure 7: Isoresistsivity map of layer 3
43
0.2467
117.72
Figure 10: Anisotropy coefficient map
W
E
a
W
High resistivity emerging
at the surface
b
Figure 11 : Pseudo-section for Wenner Profile 1
along raod 502-A (b) Profile 2 along road 502.
Figure 9: (a) Longitudinal conductance map (b)
Transverse Resistance map
44
E

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